Concise synthesis of several oligostilbenes from the enzyme-promoted oxidation of brominated resveratrol

The simple synthesis of (±)-parthenostilbenins A and B and (±)-quadrangularins A and B, as well as several unnatural resveratrol dimers, was successfully accomplished for the first time. Moreover, (±)-restrytisols B, (±)-leachianols F and G were efficiently prepared with higher yields compared with those in the literatures. The regioselective oxidative coupling reactions of 3,5-dibromo-resveratrol catalyzed by different enzymes in various solvent systems were used as key steps. The coupling mechanisms for the formation of distinct dimeric skeletons were also proposed.     

Vitamin E: Or Why We Don't Go Rancid

The authors' chemical studies on vitamin E are summarized. These studies provide very strong support for the view that vitamin E owes its biological activity solely to the fact that it acts as a general purpose, lipid-soluble, peroxyl-radical-trapping antioxidant.     

FeCl3·6H2O oxidation of protected resveratrol for the synthesis of tetraarylfuran-type oligostilbenes

Several 8-8-coupled tetraarylfuran-type oligostilbenes were prepared through FeCl₃·6H₂O-catalyzed regioselective oxidative couplings of protected resveratrol precursors. The global deprotection of the coupling dimers in a one-pot reaction yielded (±)-pallidol instead of the targets (±)-restrytisol B and (±)-tricuspidatol A.     

Preparation of silybin 23-esters ability against LPO and and evaluation of their inhibitory DNA protective properties

Twelve 23-esterified silybin derivatives with different patterns of substituents such as aromatic and aliphatic groups (1-12) were designed and synthesized. The antioxidative properties of these compounds were evaluated. The modified silybin analogues exhibited improved inhibitory effects against rat liver homogenate lipid peroxidation compared to silybin, with exception of the trimethoxylated ester (5) and the aliphatic one (9). Compounds 3, 5, 7, 8 and 11 displayed their protective properties on DNA cleavage in a dose-dependent manner.     

Fourier transform Infrared characterization of melanin free ink from selected cephalopods for identification of active functional groups responsible for antioxidant activity

The present investigation aims to explore the active functional groups that are responsible for the antioxidant property in MFI from three cephalopods such as Sepia pharaonis (CMFI), Sepioteuthis lessioniana (SMFI) and Amphioctopus aegina (OMFI) using Fourier Transform Infrared (FTIR) spectroscopy. Highest DPPH scavenging activity of 28.29 ± 0.41% and metal chelating activity of 47.62 ± 0.48% were shown by MFI from A. aegina (OMFI) at a concentration of 0.045 mg/ml and 0.04 mg/ml, respectively. Though the invitro antioxidant values of MFI were low, when added with sardine fish mince, it retarded the lipid oxidation during the entire storage period and it was very clear with the lower TBARS values compared to the control. FTIR analysis of CMFI, SMFI and OMFI revealed the presence of characteristic strong band at 3361.92 cm^?1, 3364.54 cm^?1 and 3373.96 cm^?1 and at 1642.20 cm^?1, 1636.21 cm^?1and 1635.53 cm^?1,respectively. The O–H and N–H stretching vibrations and alkenyl c = c stretch corresponding to the two vibrations in all the three spectra can be accountable for its antioxidant activities leading to its wide new applications as a natural antioxidant from marine resources.     

分子印迹在线富集-化学发光法测定葡萄酒和虎杖提取物中的白藜芦醇

制备了白藜芦醇的分子印迹聚合物,用聚四氟乙烯管作为微固相萃取柱,连接在流动注射系统的八通阀上,对白藜芦醇进行富集和分离;经甲醇和乙酸混合洗脱液(9:1,V/V)在线洗脱后与酸性KMnO4发生化学发光反应.测定白藜芦醇的线性范围2.5×10-7～6.1×10-5g/mL,方法的检出限为(3σ)8×10-8g/mL,11次...     

A novel multicommuted fluorimetric optosensor for determination of resveratrol in beer

Resveratrol (3,5,4′-trihydroxystilbene) is a phytoalexin that plays a central role in the human diet because of its antioxidant, anticarcinogenic and antimutagenic properties. This paper shows the development of a multicommuted optosensing device for the determination of resveratrol in beer. The method is based on the measurement of the fluorescence (277/382 nm, λ_ex/λ_em) of the photoproduct on-line generated by UV-irradiation of resveratrol. The fluorescent photoproduct is monitored once it is retained on a solid support (Sephadex QAE A-25) in the detection area, which improves both sensitivity and selectivity. The sample was delipidated with toluene and cyclohexane and resveratrol was extracted by solid-phase extraction (SPE) on C₁₈ cartridges, using methanol as eluent. This pre-treatment allowed recovering about an 82% resveratrol and removing its 3-O-β-d-glycoside (piceid) and other interfering substances present in beer. The method provides a detection limit (DL) of 1.0 ng mL⁻¹ and a linear dynamic range (LDR) of 3.3-100 ng mL⁻¹. It was satisfactorily applied to the determination of resveratrol in top- and bottom-fermented beers by standard addition calibration. Resveratrol concentrations in the analysed samples varied from 4.1 to 14.1 ng mL⁻¹. This is the first proposed spectroscopic method for determination of resveratrol in beer.     

Antioxidative Capacity of Irbesartan

The author investigated the antioxidant effect of irbesartan[2-butyl-3-({4-[2-(2H-1,2,3,4-tetrazol-5-yl)· phenyl]phenyl}methyl)-1,3-diazaspiro[4.4]non-1-en-4-one], an angiotensin receptor blocker(ARB), on the oxidation of erythrocytes induced by 2,2-[azobis(2-amidinopropane) hydrochloride](AAPH) and H2O2. The value of half concentration(IC50) of irbesartan to scavenge radicals was measured by reacting it with 2,2-[azinobis(3-ethylbenzothiazoline-6-sulfonate) radical cation](ABTS+·). Activities of the catala...     

5-Hexylidene-4-propylamino-1,5-dihydroimidazol-2-one formed from Cu-catalyzed oxidation with implication for the structure of a His-Lys cross-link

Cu-catalyzed oxidation of 5-hexyl-1,3-dihydroimidazo-2-one(1)in the presence of propylamine,as surrogates for the oxidized His side chain and Lys side chain,was investigated.5-Hexylidene-4-propylamino-1,5-dihydroimidazol-2-one(2),a model His-Lys cross-link product,was isolated and structurally characterized by NMR and mass spectrometry.     

An automatic optosensing device for the simultaneous determination of resveratrol and piceid in wines

For the first time, a spectrofluorimetric method is reported for the simultaneous determination of resveratrol (RVT) and piceid (PCD), two stilbenes showing diverse interesting physiological and biochemical attributes, as well as a wide range of health benefits ranging from cardioprotection to chemoprevention. The method makes use of a multicommutated flow-through optosensor in which the resolution of RVT and PCD is accomplished by means the sequential arrival of their photoproducts, on-line generated by UV-irradiation, to the detection area. This is possible due to the different kinetic behaviour of these latter on a solid support (C₁₈ silica gel) filling a minicolumn placed before the detector. The measurement in solid-phase of the photochemically induced fluorescence of the photoproducts (λ_ex: 257 nm/λ_em: 382 nm) is used as analytical signal for monitoring both compounds. The method has been applied to the analysis of RVT and PCD in wines and requires a previous solid-phase extraction (SPE) using Bakerbond C₁₈ cartridges. This pretreatment and the use of a solid-support in both the minicolumn and the flow-cell of the detector allow the determination of RVT and PCD by external calibration. Detection limits (DLs) are 9.3 and 12.6 ng mL⁻¹ for RVT and PCD, respectively. Commercial red and white wine samples have been analysed and the results obtained have been satisfactorily validated by high-performance liquid chromatography (HPLC).     

Synthesis of keratine,silver, and flavonols nanocomposites to inhibit oxidative stress in pancreatic beta-cell (INS-1) and reduce intracellular reactive oxygen species production

Flavonols (FLA) from Vaccinium macrocarpon (V. macrocarpon) were identified using high-performance liquid chromatography coupled with mass spectrometry detection. Nanoparticles were prepared using highly crosslinked keratin (KER) from human hair and silver and entrapped with flavonols [KER + FLA + AgNPs]. Nanocomposites were characterized using UV–Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction, zeta potential, and dynamic light scattering, and release profiles. The interactions between the capping agent and the silver core have been investigated using FTIR spectroscopy·H₂O₂ is a source of Reactive Oxygen Species (ROS) and acts as an activator of oxidative stress affecting NS-1 cells, and the protective effect of the nanocomposites were evaluated against H₂O₂-induced pancreatic β-cell damage. LC-MS/MS and HPLC analyses revealed the presence of 12 flavonols in V. macrocarpon plant extract. The cell apoptosis and proliferation, were evaluated by Hoechst 33342 staining, flow cytometry and Cell Counting Kit-8 respectively. Preincubation of the NS-1 cells with 250 µg/mL of H₂O₂ induced oxidative stress conditions that show pancreatic β-cell dysfunction, including ROS, cell death, mitochondrial function, antioxidant enzymes, and lipid peroxidation. Nevertheless, pretreatment with FLA and [KER + FLA + AgNPs] prevented mitochondria disruption, maintained cellular ATP levels, inhibited LDH release, intracellular ROS production, decreased lipid peroxidation, increased expression of antioxidant enzymes (CAT, SOD, and GPx) and GSH levels. These results indicate that nanocomposites could protect rat INS-1 pancreatic β-cell from H₂O₂-induced oxidative damage, apoptosis and proliferation by reducing the production of intracellular reactive oxygen species.     

Biotransformation of resveratrol: synthesis of trans-dehydrodimers catalyzed by laccases from Myceliophtora thermophyla and from Trametes pubescens

Laccases from different sources have been used, for the first time, for the selective oxidation of the stilbenic phytoalexin trans-resveratrol (3,5,4′-trihydroxystilbene, 1a) on a preparative scale. Specifically, the enzymes from Myceliophtora thermophyla and from Trametes pubescens gave the dehydrodimer 2a in 31 and 18% isolated yields, respectively. These results compare favorably with the reported data for the chemically catalyzed dimerization of 1a (18% yields). The antioxidant properties of 2a have also been investigated.     

Effect of sound wave stress on antioxidant enzyme activities and lipid peroxidation of Dendrobium candidum

The effect of sound wave stress on important medicinal plant, Dendrobium candidum Wall. ex Lindl, was investigated, including the responses on malondialdehyde (MDA) content, the activities change of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX). Results were found that the activities of SOD, CAT, POD and APX enhanced totally in different organs of D. candidum, as leaves, stems and roots, in response to the stress. Furthermore there happened similar shift of antioxidant enzymes activities, which increased in the initial stimulation and decreased afterwards. Data showed SOD, CAT, POD and APX activities ascended to max at day 9, 6, 9 and 12 in leaves, at day 9, 6, 12 and 9 in stems, and at day 12, 6, 9 and 9 in roots, respectively. As a lipid peroxidation parameter, MDA content in different organs increased in the beginning, dropped afterward, and increased again in the late. Anyway the total trend was the rise of MDA level compared to the control. It was interesting that the MDA content appeared the lowest levels almost when the antioxidant enzymes activities were up to the highest. Our results demonstrated the different organs of D. candidum might produce accumulation of active oxygen species (AOS) under initial treatment of sound wave stress. Later AOS might start to reduce due to the enhancement of antioxidant enzymes activities treated by the stress. The data revealed that the antioxidant metabolism was to be important in determining the ability of plants to survive in sound stress, and the up regulation of these enzymes activities would help to reduce the build up of AOS, which could protect plant cells from oxidative damage. Moreover, different cell compartments might activate different defensive system to reduce excessive amount of AOS. Finally the mechanism of this action was also discussed simply.     

Inhibition of Low-Density Lipoprotein Peroxidation by BHA Use: Fluorimetric Assay

Abstract

In the presence of free radicals, low-density lipoproteins (LDL) undergo oxidation that leads to the formation of lipoperoxides, which cause various damaging effects. Starting from the classical oxygen radical absorption capacity (ORAC) method, a modified method was formulated to develop a laboratory model that is able to deliver information about the use of polyphenols as nutrient supplements. The aim of this work was to establish the possible inhibition of LDL peroxidation by two different antioxidants, Trolox and BHA, and to assess if the effect is either of prevention or repair. 2,2,-Azobis(2-methylpropionamidine) dihydrochloride (AAPH) was used as free radical generator, and fluorescein was used as fluorescent probe. It was noticed that the radical scavenging effect decreases in the order BHA to Trolox to LDL itself. Trolox shows a higher efficacy against the free radicals generated by AAPH than against lipoperoxides, whereas BHA is more efficient against lipoperoxides.     

Novel biomarkers of protein oxidation sites and degrees using horse cytochrome c as the target by mass spectrometry

Biomarkers held both incredible application and significant challenge in probing the oxidation mechanisms of proteins under oxidative stress. Here, mass spectrometry (MS) coupled with liquid chromatography (LC) was applied to establish a new pipeline to probe the oxidation sites and degrees of horse cytochrome c (HCC) with its oxidative products serving as the biomarkers. Samples of native and UV/H(2)O(2) oxidized HCCs were digested by trypsin and subjected to biomarker discovery using LC/MS and tandem mass spectrometry (MS/MS). Experiment results proved that the main oxidation sites were located at Cys(14), Cys(17), Met(65) and Met(80) residues in peptides C(14)AQC(heme)HTVEK(22), C(14)AQCHTVEK(22), E(60)ETLMEYLENPKK(73), M(80)IFAGIK(86) and M(80)IFAGIKK(87). Quantitative analysis on the oxidized peptides showed the oxidation degrees of target sites had positive correlations with extended oxidation dose and controlled by residues types and their accessibility to solvent molecules. Being able to provide plentiful information for the oxidation sites and oxidation degrees, the identified oxidized products were feasibility biomarkers for HCC oxidation, compared with the conventional protein carbonyl assay.     

On the role of ethylene bridge elongation in the antioxidant activity of polyhydroxylated stilbenes: A theoretical approach

The aim of this work is to investigate the elongation effect of the conjugated links of the 7–8 double bond of trans-resveratrol and its analogs on the antioxidant activity in vacuo and water using a quantum chemistry calculation by the Density Functional Theory (DFT) method. H atom transfer (HAT), single-electron transfer–proton transfer (SET–PT) and sequential proton loss electron transfer (SPLET) mechanisms were investigated. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the spin density were calculated. The results reveal that the elongation of the conjugated links plays an important role in promoting the antioxidant properties of molecules because of its lowering effect on BDE, spin density, AIP, and PA values. The higher antioxidant activity of 3,4 dihydroxystilbene (A₄) and trans,trans-3,4-dihydroxybistyryl (B₄) may be from the abstraction of the hydrogen atoms of the ortho-position hydroxyls. This abstraction can occur continuously to form a semiquinone structure, or even a quinone structure. On the other hand, the compounds bearing the 4,4′-DHS skeleton exhibit strong antioxidant activity due to their para-quinone structure. The results indicate correspondences between the theoretical and the experimental results. Moreover, our calculations suggest that the HAT mechanism is the most important and dominant mechanism in vacuo, the SPLET mechanism is the most thermodynamically favourable pathway in water, while the SET–PT mechanism is not preferred in all the environments studied.     

Inhibition of resveratrol glucosides (REs) on advanced glycation endproducts (AGEs) formation: inhibitory mechanism and structure-activity relationship

Abstract

The study on inhibitory effects of resveratrol glucosides (REs) on advanced glycation endproducts (AGEs) formation is still unmet. Herein, for the first time, the antiglycation activities of five REs in the fetal bovine serum proteins (FBS)/fructose system were evaluated, and its structure-activity relationship and antiglycation mechanism were further explored. These REs showed remarkable inhibition toward AGEs formation. Among them, Piceatannol-3'-O-glucoside (PG) exhibited highest antiglycation activity as reflected in approximately 80% inhibition of fluorescent AGEs at the concentration of 1.0?mM. The structure-activity relationship analysis indicated that glucoside attached to the B ring of resveratrol displays a superior antiglycation activity. Moreover, the results of antiglycation mechanism showed that the antiglycation activity of REs was proportional to their antioxidant capacity and methylglyoxal (MGO) trapping capacity. Therefore, the REs are promising candidates worthy of further exploration for preventing AGEs accumulation in vivo, thereby treating AGEs-associated diseases.     

Isocratic chromatography of resveratrol and piceid after previous generation of fluorescent photoproducts: wine analysis without sample preparation

Resveratrol and its 3-glucoside (piceid), are stilbene-like molecules produced by plants. Both of them are weakly fluorescent, but highly fluorescent compounds are obtained when their hydroethanolic solutions are UV-irradiated, which implies a substantial improvement in the sensitivity of analytical methods. Experimental design (central composite design) together with the response surface methodology have been used to find optimum conditions for the fast, sensitive, and precise chromatographic analysis (with isocratic elution) of resveratrol and piceid in wine samples. These compounds have been UV-transformed into their respective photoproducts, which have been separated in a C18 column (Novapack C(18) 150x3.9 mm, 4 microm) by isocratic elution, using a mobile phase made up of acetonitrile and 4.1 vol% aqueous acetic acid, 19:81 v/v, at a flow rate of 0.8 mL/min, and fluorimetrically detected at 364 nm (lambda(exc) = 260 nm). Detection limits (S/N = 3) are 0.29 and 0.28 microg/L for resveratrol and piceid, respectively. The method has been applied to the analysis of these compounds in wine samples without a clean-up step. The analysis is completed in only 20 min. The standard addition method has been applied to the analysis of a commercial red wine and average recoveries near 100% were obtained for resveratrol and piceid. Three wine pools were satisfactorily analysed by external calibration.     

Inverse gas chromatography in the study of polymer degradation. Part 4: A study of model systems for reinforced vulcanizates

Summary Inverse gas chromatography with olefinic stationary phases, impregnated with silica gel or carbon black, and air as carrier gas has been found to yield characteristic shifts of retention data and concomitant changes in peak shape. The plots of retention index versus oxygen flow obtained indicate carbon black to have significant antioxidant properties, which are not altogether lost on solvent extraction. On the other hand, silica gel yields results consistence with the existence of a novel chain scission repair process.